Ultrasonic inspection apparatus and method for evaluating ultrasonic signals

ABSTRACT

An ultrasonic inspection apparatus for non-destructive inspection of a test body. The apparatus includes a probe, a transmitter operably connected to the probe, a receiver operably connected to the probe and a monitor with a display operably connected to the receiver for representing the echo signals received. The receiver receives echo signals. The transmitter generates transmitter pulses and delivers the transmitter pulses to the probe, wherein the probe delivers ultrasonic pulses and insonifies them at a certain angle (α) into a test body. The pulses penetrate the test body where the test pulses are at least once reflected from a rear wall of the test body forming, as a result thereof, at least one first leg that extends from an entrance surface to the rear wall and a second leg that extends from the rear wall to the entrance surface. The echo signals received are represented on the display so as to show from which leg the echo signals originate.

FIELD OF THE INVENTION

The invention relates to an ultrasonic inspection apparatus fornon-destructive inspection of a test body. The invention further relatesto a method of representing echo signals that are obtained using anultrasonic inspection apparatus for non-destructive inspection of a testbody.

DESCRIPTION OF THE RELATED ART

Suitable inspection apparatus have been known for ultrasonicnon-destructive inspection of a workpiece. Generally, the reader isreferred to the German book by J. and H. Krautkrämer, Ultrasonic Testingof Materials, sixth edition.

The angle beam probe delivers high-frequency sound pulses (about 1-10MHz) that are sent into the workpiece to be tested and are reflectedfrom the entrance surface back to the angle beam probe on the one sideand penetrate the workpiece on the other side where they are reflectedat least once from a rear wall of the workpiece. The sound waves arereflected off inner inhomogeneities such as material flaws and are againreceived by the angle beam probe and processed in the ultrasonicapparatus.

The method of the invention is suited for a plurality of currentmeasurement methods; the invention will be explained hereinafter withreference to the pulse-echo method. The angle beam probe deliversultrasonic pulses preferably periodically and later receives the echosignals of these delivered ultrasonic pulses. Generally, the echo signalfrom the entrance surface is a particularly strong signal that isstronger than the other echo signals. The other echo signals originatefrom the workpiece and more specifically from the rear wall of theworkpiece. Inasmuch, the inspection method is suited for workpieces theentrance surface of which extends substantially parallel to the rearwall so that the ultrasonic pulse is reflected several times back andforth within the workpiece.

The angle beam probe is disposed next to the to-be-tested area and thesound signal is insonified into the area of concern, from the side forexample. This is the case with ultrasonic inspection of weld seams, forexample. The ultrasound wave enters the material until it is partiallyor completely reflected from an interface. If the reflecting surface isnormal to the direction of propagation, the sound wave will be reflectedin its initial direction and will reach, after a certain travel time, apiezoelectric crystal disposed in the angle beam probe that converts thesound wave back into an electrical pulse. The return ultrasound is againreflected from the interface crystal-workpiece surface with this smallsound portion travelling a second time through the workpiece. Thus, whatis termed an echo sequence is produced by multiple reflection frominterfaces (rear wall of the part being tested or flaw) when using thepulse-echo method.

Accordingly, when the test body has no flaws, the sound is reflectedbetween the entrance surface and the rear wall of the test body andcontinues to penetrate the test body at a certain angle in the directionaway from the angle beam probe.

When inspecting weld seams, the angle beam probe is caused to move alongthe weld seam until a maximal flaw echo signal is produced. The echosignals received are directly displayed on the monitor. Generally, theyare displayed as what is termed an A-scan in which the voltage values ofthe echo signals received are plotted down the side of the scan or alongthe vertical axis whereas time is plotted on the horizontal axis. As thesound wave is reflected back and forth several times between theentrance surface and the rear wall, a sequence of uniformly spaced echosignals are produced, the amplitude of which generally decreases withincreasing time. The discrete back and forth movements, meaning thedistance the sound travels from the entrance surface to the rear walland back is referred to as a leg. Starting from the angle beam probe, afirst leg, which extends at an incline from the entrance surface towardthe rear wall, is first produced. From there, the sound is reflected,forming a second leg that extends from the rear wall toward the entrancesurface, and so on.

Because of the inclined orientation of the sound paths, the location ofa reflector (flaw) in the test piece may only be determined bygeometrical considerations and is computed on the basis of the known andmeasured data.

For a successful manual inspection of the test body, it is necessarythat the inspector scans the test bodies with constant accuracy usingthe angle beam probe. This is the only known way to achieve a resultthat is sufficiently precise. Also, this is necessary for documentingthe test later. When testing large test bodies in particular, and morespecifically, when testing long weld seams, it may happen that theinspector, lacking concentration, inaccurately follows the distance tobe scanned.

Using the prior art measurement methods, the inspector must thereforekeep an eye on the test body at all times and does not receive anyfeedback from the monitor about the position of the angle beam probewith respect to the weld seam to be tested, for example. As a result,the inspector must always alternately have a look on the monitor and onthe test body. If, for instance, he detects a flaw on the monitor, thatis to say, in the A-scan, and if he reacts too late, the inspector'shand holding the angle beam probe has already moved away from thecritical site. As the inspector only looked on the monitor, it will bequite difficult for him to find the position of concern.

SUMMARY OF THE INVENTION

The present disclosure is directed to facilitating the work of theinspector. The present disclosure aims at developing a method ofevaluating ultrasonic signals produced using an angle beam probe bywhich the inspector is already provided with additional informationduring testing so that it is easier for the inspector to inspect thetest body. The present disclosure is more specifically intended toprovide the inspector with auxiliary information that will make iteasier for him to precisely guide the angle beam probe as required.

In accordance with the present disclosure, this is achieved both by anultrasonic inspection apparatus and by a method by which the receivedelectric echo signals are represented on the display so as to show fromwhich leg they originate.

This means that the inspector can recognize at first glance whether adetected relevant signal such as a defect displayed on the monitor islocated in the region of the first, the second or another leg. Thedistance between the relevant signal and the angle beam probe can bedirectly inferred therefrom. This makes it much easier for the inspectorto inspect the test body since a look on the monitor will provide theinspector with readily understandable information about the position ofthe angle beam probe. If, during testing, the inspector sees a relevantsignal displayed on the monitor, the inspector will immediately know thedistance between the origin of the signal, the defect for example, andthe angle beam probe. This tremendously facilitates the work of theinspector.

The present disclosure is not only suited for manual testing of testbodies, it also is of assistance in the automatic scanning of a testbody by means of an angle beam probe. The reason therefore is that, at aglance on the monitor, an inspector who does not manually control thetravel of the angle beam probe immediately infers from therepresentation whether the site to be tested, such as the weld seam, islocated in the right leg of the sound path and whether, as a resultthereof, the angle beam probe is spaced the correct distance apart fromthe weld seam.

As used herein, the term flaw is not only meant literally, that is, torefer to discontinuities, but is also to be construed as a significantsignal. Accordingly, the invention also includes finding any relevantlocation in a test body.

The prerequisite for such a system is the known insonification angle andthe known wall thickness of the test body. The sound path for one legand, as a result thereof, the transition from one leg to the next or thepoint at which the sound is reflected from the entrance surface or fromthe rear wall can be readily calculated from this information.

The different representation on the monitor of the legs or of theregions corresponding to a respective one of the legs can be performedusing any suited representation method.

The portion of the measured curve that is associated with a certain legcan, for example, be marked by a particular hatching or by a particularshade of grey of the background. This means that the measured curveitself remains unchanged. The information on which leg the respectiveportion of the measured curve is based is generated by the background.

Alternatively, an additional symbol may be envisaged at those points onthe measured curve at which the sound is reflected from the entrancesurface or from the rear wall. These points correspond to thetransitions from one leg to the next. Such symbols can be alphanumericcharacters or dashed lines that intersect the measured curve forexample.

In a particularly advantageous implementation variant, the monitorcomprises a color display. Depending on the leg on which the measuredcurve is based, said measured curve may then be represented in differentcolors. The use of strong colors such as primary colors is advisablehere. Also, the background of the measured curve can be representedaccordingly in different colors. Beside LCD displays, other colormonitors such as plasma displays have proved efficient.

In another advantageous implementation variant, the angle beam probecomprises a calliper for recording the zero point position at thebeginning of the inspection procedure. This means that inspection startsat a defined location on the test body, the location being stored in thesystem. This permits relevant positions of the angle beam probe to belater reconstructed on the basis of the stored data. For this purpose,the angle beam probe comprises means that serve to indicate therespective position on the surface of the body to be tested with respectto the location at the beginning of measurement. This can be performedusing, for example, a digital camera that is solidly connected to thehousing of the angle beam probe. The digital camera is oriented so as tocapture the surface of the body to be tested. It is anticipated that thedigital camera delivers an image of the surface of the body in proximityto the very location at which a central beam of the active sound elementpasses through the surface. At intervals, an electronic image of thesurface portion which is respectively located beneath the lens of thedigital camera, which accordingly lies in the object plane, is capturedby means of this digital camera. The portion may have dimensions of afew millimeters, for example, such as 2×2 or 4×4 mm. Preferably, atgiven fixed intervals, the digital camera captures an image of therespective surface portion. The reader is referred in this context tothe application DE 100 58 174 A1 of the applicant.

Also it can be advantageous if only that region of the test body to beinspected is represented on the monitor or on the display that is ofinterest for testing. This may, for example, be the weld seam to betested. If the weld seam geometry is known and stored in the ultrasonicinspection apparatus or in the computer, both spatial limits and limitswith respect to the amplitude to be taken into consideration may beentered. If, at the beginning of the measurement, the zero pointposition has been located, the distance of the angle beam probe from theweld seam can be computed any time based on the leg length or the wallthickness and on the insonification angle. Accordingly, it is possibleto represent on the monitor, any time and independent of the position ofthe angle beam probe, the mere region of the weld seam. In this verycase, it is particularly advantageous to represent the legs differently.The reason therefore is that, if the correct distance from the weld seamis maintained, a possible flaw or a relevant signal always has to occurin the same leg and the monitor and/or the measured curve accordinglyalways has to show the same representation.

Depending on the movement of the angle beam probe, it is of coursepossible that the relevant signal has to occur in a path length of twoor three legs for example, so that the representation variesaccordingly.

At a glance on the monitor and without an additional glance on the testbody, a change in the representation will immediately tell the inspectorwhether he has moved the angle beam probe too far away from the weldseam.

It may for instance also be advantageous not to have the various legsrepresented in a particular way but to rather have a back and forthmovement, that is to say two legs joined together, represented in thesame way. Also, portions of several legs can be represented in the sameway accordingly. It is also possible to represent differently thevarious back and forth movements between the entrance surface and therear wall when inspecting a test body with an ultrasonic inspectionapparatus that is insonifying the test body. Finally, it may be sensiblenot to have the representation of the measured curve be dependent on theorigin of the measured data but to only have it determined by timewindows fixed in advance. For example, after a certain time interval,the measured curve can be represented in yellow to then be shown inanother color after a certain time.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages will become more apparent upon reviewingthe appended claims and the following non restrictive description ofembodiments of the invention, given by way of example only withreference to the drawing. In said drawing:

FIG. 1: is a schematic diagram of the sound path of an ultrasonic signaltaking departure from an angle beam probe and passing through a testbody; and

FIG. 2 shows an exemplary representation, in accordance with theinvention, of an A-scan.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional view of the basic structure of an ultrasoundmeasurement using an angle beam probe 10 as the ultrasonic measurementapparatus. The angle beam probe 10, which includes a transmitter and areceiver, is connected by a wire cable 16 to a monitor 12, which in turncomprises a display 14. It may also be envisaged to use another kind ofconnection such as a wireless connection instead of the wire cable 16.

The angle beam probe 10 is disposed on a test body 18. The test body 18here is a portion of a steel plate that is connected through a weld seam20 to a second steel plate. The test body 18 comprises an entrancesurface 22 and a rear wall 24. Between the entrance surface 22 and therear wall 24, a sound path 26 is shown by a line. Taking departure fromthe angle beam probe 20, transmitter pulses, that is to say the sound,is first insonified obliquely into the test body 18 at a predeterminedangle α, forms a first leg 28, is then reflected from the rear wall 24,forms a second leg 30, returns back to the entrance surface 22, isreflected again and forms a third leg 32 and so on. In the exemplaryrepresentation, the sound path 26 intersects the weld seam 20 in theregion of its second leg 30. It is readily possible to compute, from awall thickness 34 and the angle α, the length of a leg 28, 30, 32 or thepoint of transition from one leg 28, 30, 32 to the next.

If the sound hits a flaw 36 such as an air bubble, it is reflected as anecho signal back to the receiver depending on the orientation of theflaw. Now knowing which leg 28, 30, 32 has hit the flaw 36, theinspector can now directly infer the approximate distance between theflaw 36 and the angle beam probe 10; the inspector then at least knowsthat the flaw is located on the path portion of the corresponding leg28, 30, 32.

In another advantageous implementation variant, the angle beam probe 10comprises a calliper for recording the zero point position at thebeginning of the inspection procedure. This means that inspection startsat a defined place on the test body, this place being stored in thesystem. For this purpose, the angle beam probe 10 comprises a means 38that is solidly connected to the angle beam probe 10 and serves toindicate the respective position on the surface of the body to be testedwith respect to the position at the beginning of measurement. This maybe achieved using a digital camera that is solidly connected to thehousing of the angle beam probe. It is oriented so as to capture thesurface of the test body.

FIG. 2 is a schematic diagram showing what is termed an A-scan 40 thatis represented on the display 14 of the monitor 12. The voltage values Uin V of the echo signals received are plotted down the side of the scanon the y-axis (the voltage value axis 43) whereas time is plotted inseconds on a horizontal time axis 41 (the x-axis).

The transmitter periodically delivers transmitter pulses that cause theangle beam probe 10 to deliver short ultrasonic pulses. The variousultrasonic pulses first travel through a coupling means. A part of eachpulse is generally reflected from the entrance surface 22 and arrives asan entrance echo 42 in time before other signals in the receiver.Generally, one part of each ultrasonic pulse penetrates the workpieceand is, as already explained, reflected from the rear wall 24 andaccordingly propagates in the test body between the entrance surface 22and the rear wall 24. The illustrated measured curve 44 is obtained.Moreover, a part of the ultrasonic pulse that has penetrated theworkpiece is also reflected from defects such as the flaw 36, providedsuch defects exist.

The ultrasonic measuring apparatus, or a computer cooperating therewith,computes the positions at which the one leg 28, 30, 32 merges into thenext one, that is to say, at which the sound is reflected from theentrance surface 22 or from the rear wall 24. In accordance with theinvention, these data are employed to visually represent the variouslegs 28, 30, 32 on the display 14. As shown in FIG. 2, this may be shownby lines 46 that intersect the measured curve 44 at the correspondingplaces. Alternatively, the background of the measured curve 44 couldalso be devised according to the legs 28, 30, 32 and could, for example,be hatched or colored with different shades of grey.

The use of a color display has proved very advantageous because itallows both to simplify and to make more visible the marking of theportions of the measured curve 44 corresponding to the discrete legs 28,30, 32. The backgrounds of the measured curve 44 may then be highlightedin different colors or the measured curve 44 itself can comprisedifferent colors depending on the origin of the data originating fromthe respective one of the legs 28, 30, 32.

It may also be advantageous that only that region of the test body 18 tobe inspected is represented on the monitor 12 or on the display 14 thatis of interest for testing. This may for example be the weld seam 20 tobe tested. Both spatial limits and limits relative to the amplitudes tobe taken into consideration are entered and regarded. This means thatonly those signals are displayed that originate from either the regionof the to-be-tested weld seam 20 and/or the intensity of which exceedsthe minimal limit and/or remains below the maximal limit. This alsofacilitates the work of the inspector.

From what has been said herein above, it is obvious that the apparatusof the present disclosure, and in particular, the method of inspectingworkpieces performed therewith, are suited for serial measurement. Anexample of a serial measurement is the inspection of weld connections ofautomobile bodyworks. The inspection apparatus is first adjusted on aworkpiece or on a few workpieces prior to performing serial testing.

The present disclosure is not limited to the exemplary embodimentsdescribed but also covers all the other equivalents.

1. An ultrasonic inspection apparatus for non-destructive inspection ofa test body, the apparatus comprising: a probe; a transmitter operablyconnected to the probe, the transmitter generates transmitter pulses anddelivers the transmitter pulses to the probe; a receiver operablyconnected to the probe, the receiver receives echo signals; and amonitor with a display operably connected to the receiver forrepresenting the echo signals received, in the form of an A-scan,wherein the probe delivers ultrasonic pulses and insonifies them at acertain angle (α) into a test body, the pulses penetrating the test bodywhere the test pulses are at least once reflected from a rear wall ofthe test body forming, as a result thereof, at least one first leg thatextends from an entrance surface to the rear wall and a second leg thatextends from the rear wall to the entrance surface, wherein the echosignals received are represented on the display within the A-scan so asto show from which leg the echo signals originate.
 2. The ultrasonicinspection apparatus as set forth in claim 1, wherein the echo signalson the display are represented in a diagram in the form of a measuredcurve, with time being plotted on a horizontal axis and voltage valueson a vertical axis.
 3. The ultrasonic inspection apparatus as set forthin claim 2, wherein an alphanumeric character is associated withrespective points of the measured curve that correspond to a respectivetransition from one leg to a next leg.
 4. The ultrasonic inspectionapparatus as set forth in claim 2, wherein a line intersects themeasured curve at a respective one of respective points of the measuredcurve that correspond to a transition from one leg to a next leg.
 5. Theultrasonic inspection apparatus as set forth in claim 2, whereinportions of the measured curve that originate from a certain leg areshown on a background that is typical for a respective one of the legs.6. The ultrasonic inspection apparatus as set forth in claim 2, whereinthe display is a color display.
 7. The ultrasonic inspection apparatusas set forth in claim 6, wherein portions of the measured curve thatoriginate from a certain leg are placed on a colored background that istypical for a respective one of the legs.
 8. The ultrasonic inspectionapparatus as set forth in claim 6, wherein in the regions that originatefrom a certain leg, the measured curve is shown by a color that istypical for a respective one of the legs.
 9. The ultrasonic inspectionapparatus as set forth in claim 2, wherein in the regions that originatefrom a certain leg, the measured curve is shown by a kind of line thatis typical for a respective one of the legs.
 10. The ultrasonicinspection apparatus as set forth in claim 1, wherein the display is acolor display.
 11. The ultrasonic inspection apparatus as set forth inclaim 1, further comprising: a means for determining a respectiveposition of the probe on the surface of the test body, the means beingoperably connected to the probe.
 12. The ultrasonic inspection apparatusas set forth in claim 1, wherein only a region of the test body to betested is represented on the display that is of interest for inspection,taking into consideration limit values in terms of at least one ofamplitude and spatial limits.
 13. A method of representing echo signalsobtained using an ultrasonic inspection apparatus for non-destructiveinspection of a test body, the ultrasonic inspection apparatuscomprising: a probe, a transmitter operably connected to the probe, thetransmitter generating transmitter pulses and delivering the transmitterpulses to the probe, a receiver operably connected to the probe, thereceiver receiving echo signals; and a monitor with a display operablyconnected to the receiver for representing the echo signals received inthe form of an A-scan, the method comprising the following method steps:delivering ultrasonic pulses through the probe; insonifying theultrasonic pulses into the test body at a certain angle (α) such thatthe ultrasonic pulses penetrate the test body where the ultrasonicpulses are reflected at least once from a rear wall of the test body andform, as a result thereof, a first leg that extends from an entrancesurface to the rear wall and a second leg that then extends from therear wall to the entrance surface; and representing the echo signalsreceived on the display within the A-scan, wherein the echo signalsreceived are represented on the display so as to show from which leg theecho signals originate.
 14. The method as set forth in claim 13, whereinthe echo signals on the display are represented in a diagram in a formof a measured curve, with time being plotted on a horizontal axis and avoltage value on a vertical axis.
 15. The method as set forth in claim14, wherein an alphanumeric character is associated with respectivepoints of the measured curve that correspond to a respective transitionfrom one leg to a next leg.
 16. The method as set forth in claim 14,wherein a line intersects the measured curve at a respective one ofrespective points of the measured curve that correspond to a transitionfrom one leg to a next leg.
 17. The method as set forth in claim 14,wherein portions of the measured curve that originate from a certain legare placed on a background that is typical for a respective one of thelegs.
 18. The method as set forth in claim 14, wherein regions thatoriginate from a certain leg, the measured curve is shown by a kind ofline that is typical for a respective one of the legs.
 19. The method asset forth in claim 13, wherein the display is a color display
 20. Themethod as set forth in claim 19, wherein portions of the measured curvethat originate from a certain leg are placed on a colored backgroundthat is typical for a respective one of the legs.
 21. The method as setforth in claim 19, wherein regions that originate from a certain leg,the measured curve is shown by a color that is typical for a respectiveone of the legs.
 22. The method as set forth in claim 13, furthercomprising: a means for determining a respective position of the probeon the surface of the test body, the means being operably connected tothe probe.
 23. The method as set forth in claim 13, wherein only aregion of the test body to be tested is represented on the display thatis of interest for inspection, taking into consideration limit values interms of at least one of amplitude and spatial limits.